The present invention relates to a resist material or a chemically amplified resist material suitably used in refinement technique and a pattern formation method using the resist material.
In accordance with recent increase of the degree of integration and the operation speed of an LSI, there are increasing demands for refinement of an interconnect pattern rule.
The refinement of the interconnect pattern rule has been rapidly developed because of increased NA of a projection lens, improved performance of a resist material, a reduced wavelength of exposing light and the like.
With respect to increase of resolution and sensitivity of a resist material, a positive chemically amplified resist material using, as a catalyst, an acid generated through irradiation with exposing light exhibits high performance and hence has become a leading resist material particularly in the field of deep UV lithography (see Japanese Patent Publication No. 2-27660 and Japanese Laid-Open Patent Publication No. 63-27829).
Also, reduction of the wavelength of the exposing light from i line (of a wavelength of a 365 nm band) to KrF excimer laser (of a wavelength of a 248 nm band) has brought a large technical innovation, and a resist material for the KrF excimer laser was applied to 0.30 μm process at first and to a 0.18 μm rule in the course of time and is now applied to mass-production employing a 0.15 μm rule.
Furthermore, a 0.13 μm rule has already been studied. Thus, the speed for development in the refinement has been increasing, and hence, it is necessary to further improve transparency and substrate adhesiveness of a resist material.
It is expected that the design rule can be further refined to 90 nm or less by using ArF excimer laser (of a wavelength of a 193 nm band) as the exposing light. However, a conventionally used resin such as a Novolac resin or a poly(vinylphenol)-based resin has strong absorption in the vicinity of the wavelength of the 193 nm band, and hence cannot be used as a base polymer for a resist film in this case.
Therefore, for attaining transparency and dry etching resistance, use of an acrylic resin or a cycloolefin-based alicyclic resin as a base polymer has been examined (see Japanese Laid-Open Patent Publication Nos. 9-73173, 10-10739 and 9-230595 and International Bureau pamphlet numbered WO97/33198).
The other references related to the background of the invention are Japanese Laid-Open Patent Publication Nos. 2000-330289 and 2002-250215; Tsuyohiko FUJIGAYA, Shinji ANDO, Yuji SHIBASAKI, Mitsuru UEDA, Shinji KISHIMURA, Masayuki ENDO and Masaru SASAGO, “New Photoresist Material for 157 nm Lithography-2”, J. Photopolym. Sci. Technol., 15(4), 643-654(2002); and Polymer Handbook 4th Edition, 11-309, Wiley-Interscience.
An acrylic resin has, however, a problem that a resultant resist pattern is in a poor shape when it is used as a base polymer because it swells in development, and an alicyclic resin has a problem that solubility in a developer and substrate adhesiveness are degraded when it is used as a base polymer because it has a strong hydrophobic property.
On the other hand, F2 laser (of a wavelength of a 157 nm band) is expected to attain refinement of the design rule to approximately 65 nm or less, but it is difficult to attain sufficient transparency of a base polymer. It has been found that an acrylic resin that is used as a base polymer in using ArF excimer laser does not transmit the F2 laser at all, and that a cycloolefin-based resin having a carbonyl bond has strong absorption against the F2 laser. Furthermore, poly(vinylphenol), which is used as a base polymer in using KrF excimer laser, has an absorption window (namely, a region that has high transparency because exposing light is not absorbed therein) in the vicinity of a wavelength of a 160 nm band, and hence the transmittance is slightly improved when it is used, but it has been found that the transmittance is still far from practical level (that is, transmittance of 40% or more).